If the state were to pass such a measure, it would be likely to face a court challenge, and courts have consistently ruled that states cannot nullify federal laws.

But sponsoring Sen. Brian Nieves, R-Washington, said the bill would protect law-abiding gun owners from federal encroachments and regulations. Missouri Republicans began pushing for the legislation following President Barack Obama's call last year for increased background checks and a ban on assault weapons.

The measure also would designate school personnel to carry a concealed weapon in school buildings after undergoing training.

Opponents argue that would increase access to firearms, which could then lead to more instances of gun violence.

"I cannot support this legislation in good conscience," said Sen. Jamilah Nasheed, D-St. Louis. "Kids are killing kids in school."

School districts would need to hold a public meeting before allowing personnel to carry in buildings. Designated personnel could also carry pepper spray instead of a weapon.

Another provision of the bill would let holders of concealed gun permits carry firearms openly, even in municipalities with ordinances banning open carry. It would also lower the minimum age to get a concealed weapons permit to 19, down from 21. Under the bill, health care professionals could not be required to ask or document whether a patient owns a firearm.

Democratic Gov. Jay Nixon vetoed a similar measure that the Republican-controlled Legislature passed last year.

Nieves' bill is less specific than last year's version about which federal laws it seeks to nullify. It removes references to the 1934 and 1968 gun control acts, while keeping generic references to fees, registration and tracking policies that are considered "infringements" or "have a chilling effect on the purchase or ownership" of guns and ammunition by law-abiding citizens.